The invention relates to a sheet-fed printing machine having at least one feed system for feeding sheets thereto from a feeder, the sheet-fed printing machine having at least one front lay serving to align the leading edge of the sheets to be processed, and a method of operating the sheet-fed printing machine.
The published German Patent Document DE 195 03 739 C1 reveals a sheet-fed printing machine of the type mentioned hereinbefore. It has, amongst other components, a feeder, a front lay, a pre-gripper including a gripper bar, and a feed cylinder. The front lay and the gripper bar are constructed so as to be pivotable and are coupled to the drive of the sheet-fed printing machine so as to be displaced at the cycle rate of the machine. The stacked sheets are separated in the feeder and subsequently aligned by the front lay so that the leading edge thereof extends exactly transversely with respect to the transport direction of the sheets. At the front lay, the sheet is gripped by the gripper bar and transported onwards to the feed cylinder. When preparing for a new print job, wherein a new printing image is to be printed onto the sheets, the feeding of the sheets in the feeder is stopped and at least one plate cylinder within the sheet-fed printing machine has an image set thereon directly with the aid of a laser, in an inkjet method, by thermal transfer or the like. During the setting of the image or imaging operation, the drives of the sheet-fed printing machine continue to run operatively, as well, the feed roller, amongst others, thus rotating at machine speed, and the front lay and the gripper bar being displaced oscillatingly at a corresponding speed. As a result of the movements of the front lay and the gripper bar, oscillations are introduced into the machine and tend to disrupt the setting of the image on the plate cylinder. It is often the case that, in order to set the image, the machine speed is increased to such an extent that it corresponds to a printing throughput of 16,000 sheets per hour or more, for example. As a result, the oscillations produced by the oscillating pre-gripper and front lay are further amplified.
It is therefore an object of the invention to provide a sheet-fed printing machine of the type mentioned at the introduction hereto, and a method that can be implemented therewith, wherein disruptions caused by oscillations during the setting of an image or imaging operation can be avoided, at least to a great extent.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a sheet-fed printing machine having a feed system for feeding sheets from a sheet feeder to the sheet-fed printing machine, and an imaging device for setting an image on a printing plate disposed on the plate cylinder, the feed system comprising at least one oscillatingly moving pregripper and a drive device for the feed system, the pregripper being uncoupled from the drive device.
In accordance with another feature of the invention, the sheet-fed printing machine includes a lever mechanism for driving the pregripper.
In accordance with a further feature of the invention, the pregripper has at least one gripper bar which is displaceable at the cyclic rate of the printing machine.
In accordance with an added feature of the invention, the displacement at the cyclic rate of the printing machine is non-uniform.
In accordance with an additional feature of the invention, the displacement at the cyclic rate of the printing machine is in an oscillatory manner.
In accordance with yet another feature of the invention, the pregripper is disposed between the sheet feeder and a feed cylinder.
In accordance with yet a further feature of the invention, the sheet-fed printing machine includes a blocking device for blocking the lever mechanism in a given functional position.
In accordance with yet an added feature of the invention, the drive device is constructed as a cam drive having at least one cam disk connected to a drive shaft so as to be fixed against rotation relative thereto, the cam disk cooperating with a first pivoting lever of the lever mechanism, and being pivotable about a fixed axis.
In accordance with yet an additional feature of the invention, the sheet-fed printing machine includes a pressing device for pressing the first pivoting lever against the cam disk.
In accordance with still another feature of the invention, the lever mechanism has a second pivoting lever connected to a shaft for the pregripper so as to be fixed against rotation relative thereto, and a gripper bar is fixed to the pregripper shaft.
In accordance with still a further feature of the invention, the pressing device is in cooperative engagement with at least one of the pregripper shaft and the second pivoting lever.
In accordance with still an added feature of the invention, the first and the second pivoting levers are articulatedly connected to a coupling element.
In accordance with still an additional feature of the invention, the first pivoting lever has at least one supporting roller which, in a non-blocked state of the lever mechanism, rolls on the cam disk, the supporting roller, in a blocked state of the lever mechanism, being located at a given distance from the rotating cam disk.
In accordance with another feature of the invention, the gripper bar has at least one gripper, and the feed system includes a feed cylinder formed, for the at least one gripper, with a respective circumferential groove into which the at least one gripper is dippable as it approaches the feed cylinder.
In accordance with a further feature of the invention, the gripper bar has a plurality of grippers, and the feed system includes a feed cylinder formed, for the plurality of grippers, with a plurality of respective circumferential grooves into which the grippers, respectively, are dippable as they approach the feed cylinder.
In accordance with an added feature of the invention, a respective circumferential groove is of such depth that even when the at least one gripper is at a minimal distance from the axis of rotation of the feed cylinder, there is an interspace between the at least one gripper and the bottom of the respective circumferential groove.
In accordance with another aspect of the invention, there is provided a sheet-fed printing machine having a feed system for feeding sheets from a sheet feeder to the sheet-fed printing machine, and an imaging device for setting an image on a printing plate disposed on a plate cylinder, the feed system comprising at least one reciprocatingly pivotable front lay and a drive device for the front lay, the front lay being uncouplable from the drive device.
In accordance with a further feature of the invention, the sheet-fed printing machine includes a displacement device having a lever mechanism which is displaceable by the drive device.
In accordance with an added feature of he invention, the displacement of the lever mechanism is non-uniform.
In accordance with an additional feature of the invention, the displacement of the lever mechanism is in an oscillating manner.
In accordance with yet another feature of the invention, the drive device is constructed as a cam drive having at least one cam disk connected to a drive shaft so as to be fixed against rotation relative thereto, the cam disk cooperating with a roller lever, and being pivotable about a fixed first pivot shaft.
In accordance with yet a further feature of the invention, the lever mechanism has a coupling rod articulatedly connected to a roller lever and a lever arm having the front lay and being pivotable about a fixed second pivot shaft.
In accordance with yet an added feature of the invention, as viewed in vertical direction, in a raised position of the coupling rod, the front lay is displaceable into an aligning position and, in a lowered position of the coupling rod, is displaceable into a standby position.
In accordance with yet an additional feature of the invention, the sheet-fed printing machine includes a pressing device assigned to the lever mechanism for applying a force to the lever mechanism so that at least one supporting roller of the roller lever is pressed against the cam disk.
In accordance with still another feature of the invention, the sheet-fed printing machine includes a blocking device assigned to the lever mechanism by which the coupling rod can be raised to such an extent that the roller lever is out of contact with the cam disk.
In accordance with still a further feature of the invention, at least one imaging device is integrated into the sheet-fed printing machine.
In accordance with an added aspect of the invention, there is provided a method of operating a sheet-fed printing machine having a feed system for feeding sheets from a feeder to the sheet-fed printing machine, which comprises providing an imaging device for setting an image on a printing plate disposed on a plate cylinder, and uncoupling parts of at least one of the feeder and at least one feed system for transporting the sheets from a drive, while the image is being set on the printing plate.
In accordance with a concomitant mode, the method of the invention comprises uncoupling at least one of a gripper bar of a pregripper and a front lay from the drive.
The sheet-fed printing machine according to the invention thus has at least one feed system for feeding sheets from a feeder to the sheet-fed printing machine, and a drive device for the feed system. The sheet-fed printing machine is distinguished by the fact that the feed system can be uncoupled from the drive device. It is therefore possible to ensure that, for example, during the setting of an image on a printing device, in particular a printing plate or a plate cylinder, the feed system is, so to speak, stopped, so that with the machine running or the drive running, no oscillations which could disrupt the setting of an image are produced by the feed system.
In an advantageous exemplary embodiment of the sheet-fed printing machine, the feed system has a pregripper that can be driven with the aid of a lever mechanism and preferably has at least one gripper bar which can be displaced at the cyclic rate of the machine. The drive device can co-operate directly with the lever mechanism here, i.e., the lever mechanism can be uncoupled from the drive device. The gripper bar can be displaced, for example, non-uniformly or in an oscillatory manner.
In a preferred embodiment, the lever mechanism can be blocked in a specific functional position with the aid of a blocking device, i.e., the lever mechanism can be stopped during the operation of the sheet-fed printing machine. In order, at the same time, to rule out any damage to the drive and to the lever mechanism, for example, a clutch can be provided between the lever mechanism and the drive.
In a particularly advantageous exemplary embodiment, the drive device is constructed as a cam drive, which has at least one cam disk firmly connected to a drive shaft so as to rotate therewith and which cooperates with a first pivoting lever belonging to the lever mechanism, and can be pivoted about a fixed axis. The functional position, wherein the lever mechanism can be blocked in this exemplary embodiment, so as to prevent an oscillatory movement of the gripper bar, has preferably been reached when that part of the lever mechanism which cooperates with the cam disk during the printing of the sheets is at its greatest distance from the axis of rotation of the cam disk. Therefore, in spite of the blocking of the lever mechanism, the cam disk can continue to rotate, without resulting in any damage to the lever mechanism.
In an advantageous embodiment of the sheet-fed printing machine, the blocking device is constructed so that it cannot only block the lever mechanism, i.e., prevent it from moving, but can also move the lever mechanism at least to such an extent that there is a distance X between the cam disk and that part of the lever mechanism which rolls on the cam disk, for example, a supporting roller. When the lever mechanism is blocked, the rotating cam disk is therefore out of contact with the mechanism, so that, in the uncoupled state, no wear occurs on the cam disk or the lever mechanism. The distance X may be very small and, for example, may be 2 mm to 3 mm.
According to a development of the invention, provision is made for the first pivoting lever to be capable of being pressed against the cam disk with the aid of a pressing device. The pressing device prevents the first pivoting lever from lifting off the cam disk. The pressing device therefore acts upon the lever mechanism with a spring force, counter to which the cam disk displaces the lever mechanism in order to displace the gripper bar in an oscillatory manner. The pressing device can include, for example, a pull rod which cooperates with a spring element, for example a cylindrical helical spring, and is effectively connected to the lever mechanism. It is also conceivable for the pressing device to have a pneumatic piston/cylinder unit.
In order to achieve the objective of the invention, a sheet-fed printing machine is therefore proposed which has at least one front lay thst serves to align the leading edge of the sheets to be processed and that can be displaced at the cyclic rate of the machine by a displacement device that can be driven by a drive device. The sheet-fed printing machine is distinguished by the fact that the displacement device can be uncoupled from the drive device. Based upon this configuration, it is possible to ensure that, in the uncoupled state, the displacement device can be brought to a standstill with the machine running. This is particularly advantageous when setting an image on a plate cylinder or the like with the sheet-fed printing machine running, by an imaging device preferably integrated in the sheet-fed printing machine, because oscillations produced by the front lay or the displacement device, which could disrupt the setting of an image, are avoided.
In an advantageous exemplary embodiment of the sheet-fed printing machine, the displacement device has a lever mechanism which can be displaced by the drive device, preferably non-uniformly or in an oscillatory manner, this mechanism being actable upon with a torque by the drive device, which is preferably formed by the machine drive, and can be uncoupled from the drive device.
Particularly preferred is an exemplary embodiment of the sheet-fed printing machine wherein at least one imaging device is integrated in the sheet-fed printing machine. The imaging device is therefore a part of the sheet-fed printing machine, so that setting an image on a printing device, which, for example, can have a plate cylinder that can be driven and has a printing film, can be performed directly in the sheet-fed printing machine. The imaging device can, for example, have at least one device for performing a thermal transfer and/or an inkjet method and/or a laser device or the like.
In order further to achieve the objective of the invention, a method of operating a sheet-fed printing machine is provided which is distinguished by the fact that while an image is being set on a printing device integrated in the sheet-fed printing machine, parts of a feeder and/or at least one feed system for transporting the sheets are uncoupled from the drive. This makes it possible to ensure that these devices do not produce any oscillations which could be introduced into the sheet-fed printing machine and have a disruptive effect upon the setting of an image on the printing device which, for example, has a plate cylinder.
According to a development of the invention, provision is made that, while setting an image on the printing device preferably formed by a plate cylinder, a gripper bar of a pregripper and/or a front is or are uncoupled from the drive. The gripper bar and the pregripper are preferably at a standstill so that these devices do not produce any oscillations. It becomes clear that, in this connection, uncoupling the drive is understood to mean separating the gripper bar and/or the pregripper from the machine drive, so that, during imaging or the setting of an image, other, in particular rotating components or devices in the sheet-fed printing machine, such as a feed cylinder, guide rolls, a plate cylinder or the like, can continue to run at a non-reduced speed (printing speed) or an increased machine speed (imaging speed).
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a sheet-fed printing machine and method of operation, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein: